WASHINGTON, D.C. ( TheStreet) --The U.S. government bolstered its flu defenses Thursday night with orders for intravenous versions of Roche's Tamiflu and GlaxoSmithKline's ( GSK) Relenza.

The new orders -- 10,000 courses of each drug with an option to purchase more -- will be added to the national flu drug stockpile set up to treat seriously ill and hospitalized H1N1 flu patients.

Earlier Thursday, BioCryst Pharmaceuticals ( BCRX) said it shipped 10,000 courses of its intravenous flu drug peramivir to the U.S government, also with an option to acquire more. The announcement sent shares of the company sharply higher.

But the government's decision to purchase intravenous versions of Tamiflu and Relenza -- both of which are less expensive than peramivir -- could be seen by investors Friday as a setback to BioCryst.

Until Thursday night, it was widely believed that BioCryst's peramivir would be the only intravenous flu drug available.

Tamiflu, Relenza and peramivir are antiviral drugs that all act against the flu virus in similar ways. Tamiflu (as a pill) and Relenza (as an inhaled mist) are already approved by the U.S. Food and Drug Administration and widely used. Peramivir has not undergone pivotal studies yet and is not FDA approved. Regulators have made the drug available to doctors during the H1N1 flu pandemic under an emergency use authorization.

The U.S. Department of Health and Human Services ordered 10,000 courses each of intravenous Tamiflu, Relenza and peramivir, with an option to order another 30,000 courses of each.

The government is paying an average of $450 per course for intravenous Tamiflu and Relenza, according to a story in the New York Times. Thursday, the government said it would purchase peramivir at a price of $2,250 per course of treatment.

The FDA has not yet approved intravenous versions of Tamiflu and Relenza so the government's order is contingent on regulators granting an emergency use authorization for the drugs. This is the same process, however, by which FDA allowed the government to purchase peramivir.

-- Reported by Adam Feuerstein in Boston

Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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